fix(book-fold-phone): centre the default lens row as the manifest declares

[aldoruizluna]

What changed

Both twins now place the default lens row where the manifest declares it.

param	mode(s)	manifest default	source literal (before)	source literal (after)	file:line
lens_first_center_x	device, cover_half, camera_half, hinge	47.808	47.736	47.808	main.py:182 (PARAM fallback)
lens_first_center_x	graph_device	47.808	47.736	47.808	bookfold.graph.json:57 (lenswindow_lens_place.x, the manifest binding)

Direction and why

The source now matches the manifest default.

• 47.808 is the centred row: lens_island_center_x − lens_pitch_x·(lens_count−1)/2 = 56.88 − 9.072.
• All 27 of 27 device presets that set the lens row follow exactly that rule. I checked this with a script: zero exceptions.
• 47.736 left the default row 0.072 mm off-centre on the island. Studio sends the manifest value, so users already see the centred row.

How this maps to GOC-1

GOC-1 (Digital Twins MES, Phase 2) variables.json is only complete once yantra4d injects every declared parameter (RENDER_INJECT_FULL_PARAMS). This PR removes both default-drift notes for this cartridge (rule from hyperobjects-spec#30), on CadQuery and on the graph.

Evidence

Tooling: hyperobjects-spec at 510efba (the #30 branch; CI pins 3ff3736, which lacks the rule), CadQuery 2.8.0, macOS.

$ y4d-spec check ./book-fold-phone
y4d-spec check: cartridges=1 failures=0 notes=0 ...            # before: notes=2 (default-drift lens_first_center_x, py + graph)

$ y4d-spec check ./book-fold-phone --render --require-openscad --parity --openscad-path libs --openscad-path . -v
       (device, camera_half, cadquery): ok — volume 43302.81mm³, 1 body/bodies, watertight
       (graph_device, camera_half, graph): ok — volume 43302.81mm³, 1 body/bodies, watertight
  ok book-fold-phone (./book-fold-phone, 279 render(s) verified (270 preset), no comparable pair)
y4d-spec check: cartridges=1 failures=0 notes=84 geometry=verified renders=279 presets=270 skipped=0 parity=0/0 ok, ...

The 84 notes break down as follows. None is a default-drift note and none involves the lens:

• 66 are printability measurements (overhang and thin-wall).
• 18 say that the fold-state-* presets render the flat cover_half and hinge parts identically to the defaults. These presets set only fold_angle, which by design does not change an isolated flat part.

The CadQuery and graph twins still agree on every default part; for example, camera_half is 43302.81 mm³ on both. verification is unchanged. One cartridge, two files.

macOS green is not proof (AGENTS.md rule 4). The CI Linux render lane decides, and it is pending at the time of writing.

CI status (updated)

Linux CI on this head: manifest conformance (all cartridges): pass; render (cartridges changed in this PR) (book-fold-phone): pass; render scope: pass.

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